The only problem right now, if you want to build, is getting a barrel (assuming you install the barrel yourself). Buddy waited 4 months for a barreled upper assembly. You can find uppers at gun shows, but they're m4gery length, and run $550 and up - without the bolt carrier and bolt. I saw a parts kit for $130 the other day at a show, and a stripped lower was $180 (cheapest one I saw). Add in everything, and you're talking over 1000 - plus some potentially long wait times.
Q - What is Bambi?
A - Viable Target
I like: Bushmaster , DPMS , & Rock River Arms !!! The only big thing with Colt is, that some of there parts are oddball sized. So, you can't just find parts anywhere.
I built two about 6 months ago before parts were really scarce, a 16 and a 20. I decided I was going to build mine to save some loot. I was a little hesitant when I opened up the parts group and saw all of the little springs and stuff, but with a little research they went together pretty easy. The receivers were ordered and the rest of the parts were aquired at a show, saved alot on shipping that way. The uppers were bought already assembled as a kit and included bolt, carrier, and furniture. After they were put together I figured up the cost and I ended up saving about $800 between the two, as opposed to buying them local at a show or local shop. That saved money allowed me to buy Pmags, and some other items.